This invention relates to hydroextracting compositions for wet and finely pulverized ores and, more particularly, it relates to compositions for use for producing wet concentrated ores having a lower moisture content.
The wet and finely pulverized ores obtained in various ore concentration processes (such as the froth flotation, gravity concentration and like processes) are usually dehydrated or hydroextracted by filtration. The moisture content of the finely pulverized ores thus obtained varies in a wide range depending upon the kind of ore, the form of the particles, the surface property of the particles, the method used for dehydration, etc. For example, the wet and finely divided ores obtained in froth flotation (i.e., the flotation concentrate) are dehydrated by any known method to produce a cake of finely pulverized ores having a moisture content of about 10 - 15% by weight of the total. It is preferred to decrease the moisture content of the cake as much as possible, because (1) water in the concentrated ores increases the amount of the cake, resulting in the increase of the transportation cost, especially when the cake is transported by ship, (2) the water causes an unbalancing of a ship which is laden with the ores, (3) concentrated ores containing a great amount of water form a slurry which flows out of the containers used in the transportation, and (4) such a slurry may freeze in the winter in cold areas, resulting in difficulty in handling.
Heretofore, there have been made various attempts to produce concentrated ores having a low moisture content from wet and finely pulverized ores. For example, one attempt has been made to evaporate moisture by heating the wet concentrated ores after filtering. This method requires a large amount of fuel or petroleum, resulting in an increase of the production cost, and, in addition, brings about the generation of poisonous gas (SO.sub.2) in the case of sulfide ores. Another physical method comprises allowing the finely pulverized ores to stand in the air for a long period of time. This is not efficient, and the resultant ores on the surface of the pile become so dry that they are blown off causing air pollution.
There have been proposed some chemical methods for the hydroextraction of finely-divided substances other than the finely pulverized ores, which methods comprise adding a certain chemical agent to the wet substances and filtering the mixture. It has been suggested, for example, that some anionic surface active agents (such as alkylbenzene sulfonates, sodium dioctyl sulfosuccinates and polyethylene glycol-type nonionic surface active agents) may be used for the hydroextraction of finely divided coal or silica, but these agents are not practically effective in the hydroextraction of finely pulverized ores. In some cases, these agents have an adverse affect on the hydroextraction, resulting in the increase of moisture content of the ores. Moreover, these surface active agents have a tendency to move to the filtrate during the filtration. Such filtrate cannot be reused for the froth flotation which is adversely affected by the agents, and it cannot be discharged into a river or sea without removing the agents therefrom which may cause water pollution problems.